Apple TV: XBMC
XBMC is another program installed on the Apple TV using ATV USB Creator. XBMC is basically an open source media center application for a number of platforms.
After putzing around with XBMC for a bit, I realized it forms the foundation for Boxee. However, Boxee has added a much more elegant interface, more content options (Hulu in particular), and some social networking aspects. Therefore, Boxee surpasses XMBC in several ways.
So while it’s been nice to have XBMC on the Apple TV, I’ve hardly used it. Right now it only exists as an opportunity to fool around with a different user interface.